In prior art, sensors for detecting users, such as infrared sensors, are installed in urinal or toilet to traditionally realize automatic flushing after the users finish the using of urinal or toilet. However, the infrared sensors have many defects:
On one hand, most of the traditional infrared sensors adopt the active sensing mode, namely the infrared emitting device emits the infrared rays having limited wave length; the infrared receiving device receives the reflected infrared rays after the infrared rays are reflected by human body, and then the judge of automatic sensing is realized based on the intensity of the reflected signal. However, the automatic sensing is difficult to be performed when the infrared ray irradiates on some objects (such as black clothing, hair so on) that having low reflectivity. After the infrared light emitted by the infrared emitting device is reflected by the subjects having low reflectivity, few reflected infrared is received by the infrared receiving device. The sensor could not detect the existence of the target objects having low reflectivity because the reflected signal is too weak. Thus, malfunction of the infrared sensor will be caused.
On the other hand, after the traditional infrared sensor detects that the user has used urinal or toilet for a period of time, and then detects that the user leaves, the toiler or urinal will be cleaned with a certain mount of water. However, the automatic flushing system, which flushes based on whether the user is detected in the detected area or not, will flush with a certain mount of water regardless whether the user uses the urinal or toilet and regardless of the volume of the urine. This way, lots of water is wasted.
In prior art, conductive sensor is used to detect the change of the conductivity of the liquid in the trap of the urinal. As the urine's conductivity is different from that of the water, if the urine flows into the trap and the electrode of the conductive senor touches the urine, the detected conductivity will change. When it is detected that the urine flows into the trap, the urinal will be controlled to flush. The conductive senor overcomes the defects of using sensing window of the traditional infrared sensor, as well as overcomes the malfunction to the things having low reflectivity in the traditional infrared senor or other defects.
However the surface of the electrode of the conductive senor will be covered by the deposited ordure because the conductive sensor touches the urine for a long time. Thus, the detecting performance of the conductive sensor will be affected and the sensing malfunction will be caused.
Therefore, it is necessary to improve the conductive sensor.